Computer systems are usually configured to have their expansion units with respective power supply units sequentially and additionally provided externally to the basic units.
Therefore, when the power supply to system CPUs connected to the basic power supply is severed due to an emergency, it is necessary to cut off power supply units for all the expansion units in association with the basic power supply units.
A power supply device as shown in FIG. 1 has been proposed. A basic power supply unit 12-0 is supplied with an alternating current electric power through a circuit breaker (emergency power supply cut-off switch) 10-0 and a filter 28-0.
The expansion power supply units 12-1 through 12-n are sequentially and additionally provided externally to the basic power supply unit 12-0 and are supplied with alternating current electric power respectively via filters 28-1 through 28-n and mainline switch circuit breakers 10-1 through 10-n (power supply switches).
The direct current outputs from main power supply circuits 14-0 and 14-1 through 14-n are supplied respectively to the basic unit and expansion units of the system 29-0 through 29-n comprising CPUs.
The above basic power supply unit 12-0 and the expansion power supply units 12-1 through 12-n are equipped with the main electric power circuits 14-0 and 14-1 through 14-n as well as internal power supply circuits 16-0 and 16-1 through 16-n, and are respectively configured to convert alternating current electric power externally supplied via the circuit breaker (emergency power supply cut-off switch) 10-0 and the circuit breakers (power supply switches) 10-1 through 10-n into direct currents.
Furthermore, the internal power supply circuits 16-0 and 16-1 through 16-n are respectively provided with relay coils 18-0 and 18-1 through 18-n, which are magnetically excited upon receipt of control signals from external controllers 31-0 through 31-n after the internal power supply circuits 16-0 and 16-1 through 16-n receive external alternating current electric power. The control circuits 31-0 through 31-n are connected to consoles 32-0 through 32-n.
In addition, relay contacts 20-0 and 20-1 through 20-n are respectively provided at the alternating current power input terminals of the main power supply circuits 14-0 and 14-1 through 14-n and are driven to close respectively by the magnetic excitations of the relay coils 18-0 and 18-1 through 18-n.
Here, the external alternating current electric power input to the basic electric power unit 12-0 is supplied also to the internal power supply circuits 16-1 through 16-n of the expansion power supply units 12-1 through 12-n.
Hence, when the circuit breaker 10-0 is opened, the relay coils 18-0 and 18-1 through 18-n of the internal power supply circuits 16-0 and 16-1 through 16-n are cleared of magnetic excitations, and the relay contacts 20-0 and 20-1 through 20-n are opened.
Accordingly, the external alternating current electric power supplies to the main power supply circuits 14-0 and 14-1 through 14-n are cut off and their operations are controlled to stop all at once.
Although separate and independent external alternate power supplies are connected to the main power supplies of the basic power supply unit and the expansion power supply units in this configuration, since the external alternate electric power supplied to the basic power supply unit 12-0 is all shunted to the main power supply circuits 14-1 through 14-n of the expansion power supply units 12-1 through 12-n and the current capacity of the basic power supply cannot be increased infinitely. Thus, the number of the expansion power supply units 12-1 through 12-n cannot be increased indefinitely.
To solve the above problem, a power supply device shown in FIG. 2 has also been proposed.
In the proposed device, pairs of emergency cut-off switch driving relay coils 22-1 through 22-n and emergency cut-off relay contacts 24-1 through 24-n are provided for the expansion power supply units 12-1 through 12-n.
The respective emergency cut-off switch driving relay coils 22-1 through 22-n are magnetically excited by the internal power supply circuits 16-0 and 16-1 through 16-n-1 of the power supply units 12-0 and 12-1 through 12-n-1, which become the preceding stages of the additionally provided power supply units. The relay contacts 24-1 through 24-n are respectively driven to close by the magnetic excitations.
Thus, when the power supply to the internal power supply circuit 16-0 of the basic power supply unit (12-0) is cut off, its output is turned off, the power supply to the emergency cut-off switch driving relay coil 22-1 in the expansion power supply unit of the next stage is turned off, and the emergency cut-off relay contact 24-1 in the expansion power supply unit 12-1 opens. Therefore, when the circuit breaker 10-0 is opened, the external alternating current electric power supplies to the main power supply circuits 14-0 and 14-1 through 14-n are sequentially cut off.
The proposed device has its power supply load distributed over the present and succeeding stages additionally provided, because the power supply units 12-0 and 12-1 through 12-n 1 output direct currents to the present and succeeding stages.
Thus, it becomes possible to externally provide expansion power supply units 12-1 through 12-n, with no limit, to the basic power supply unit 12-0.
The above proposed device does not allow maintenance or inspection for only the desired expansion power supply unit (i.e. system's expansion unit), because when any of the circuit breakers 10-0 and 10-1 through 10-n are opened, all the power supply units in the stages after the one in which the circuit breaker is opened, are cut off.